1. Field of the Invention
This invention relates to an information writing device for writing the information on a disc-shaped recording medium used on being mounted on a disc driving device.
2. Description of Related Art
In a disc driving device, employing a disc-shaped recording medium, such as a hard disc, a flexible disc, an optical disc or a magneto-optical disc, a head is moved to a target track, based on the servo information written from the outset as the head positioning information on the disc-shaped recording medium, for correctly positioning the head by closed loop control.
Conventionally, a so-called servo track writer, writing the servo information on a magnetic disc, such as a hard disc or a flexible disc, is designed and constructed so that the magnetic disc is rotated at a high speed by an air spindle motor, having a high axis shake precision, the magnetic head, loaded on a head slider, is positioned on the disc from track to track by a positioner employing a high precision scale, such as a laser encoder, the servo information is written by the magnetic head and, when the servo information for one round, that is, for one complete track, is written, the head slider is radially moved along the radius of the disc a distance corresponding to one prescribed track pitch, to write the servo information for the next track, and so on, until the servo information is written in the entire track.
At this time, circumferential position detection is needed. The routine practice is to record clock signals on the disc by a separately provided magnetic head, to detect these clock signals and to re-record clock signals on the disc.
For raising the servo information write efficiency, there has also been proposed, for a servo track writer in which a plural number of discs are stacked together, and the same plural number of heads, associated with the recording surfaces of the stacked discs, are provided for writing the servo information simultaneously on the recording surfaces of the discs, a method comprising providing a master disc, on which the servo information has been written to high precision, causing the rotation of the master disc and the discs, on which the servo information is to be written, by a spindle motor, as the master disc and the discs are stacked together, and to perform head positioning control based on the servo information read out from the master disc (see, for example, Cited Reference 1). [Cited Reference 1] Japanese Patent Application Laid-Open No. 2003-162874
Meanwhile, in the method employing the master disc, having the servo information recorded thereon to high precision, it is necessary to provide a master disc, free of defects, each time the disc format is changed. Moreover, crash of the master disc may be caused in the course of the information write operation.
Moreover, the servo track writer is used in a clean room. Thus, if a magnetic clock head is used for reading out clock signals, crash of the magnetic head for clocks tends to be produced on deposition of dust and dirt on the surface of the clock head to contaminate the inside of the clean room.
Recently, with the progress in the art of recording and/or reproduction, the tendency is towards a high density recording for the recording mediums, such that the clock frequency of data recorded on the disc-shaped recording medium is becoming higher. If, in order to raise the clock signal density further, the clock frequency of the data is increased, there may be presented the problem of unneeded radiation and signal attenuation in the transmission system of the servo information.